De-Sludging ASP.NET Pages with PageAdapter

July 9, 2007

Introduction

You know what VIEWSTATE is? It's that encrypted gobbley-gook in a hidden field that makes stateless web pages (in ASP.NET) keep track of a page for each user between round trips to the server. VIEWSTATE is what keeps track of the text you put in a TextBox. VIEWSTATE is what keeps track of events that need to fire. And, VIEWSTATE is a lot of scrambled eggs that goes back and forth between each client and your server (or servers).

By now, you have probably heard that one should disable VIEWSTATE in ASP.NET applications for static content or when you know you don't need it. This is a tip for improving performance. For static web sites, this is a good tip. For dynamic websites—applications—VIEWSTATE is pretty hard to do without. However, this doesn't mean you have to card it around with each page.

In this article, I will show you how to use VIEWSTATE but leave it on the server. The technique was introduced in ASP.NET 2.0. It's a great technique, will significantly reduce the size of the rendered HTML returned to clients, still permit VIEWSTATE dependent behaviors to work, and make your web pages a little snappier.

Implementing a Custom PageAdapter

The web scales because each client gets its data and disconnects. Things such as Session ID, cookies, and VIEWSTATE help web servers figure out what to do when a page is posted back. Content-only (or content-mostly) sites like http://www.softconcepts.com don't really need a lot of state information, so it can be turned off to improve performance a bit. Further, sites like mine can use page caching to get a little better performance.

By implementing a custom PageAdapter, you can use VIEWSTATE but ASP.NET will use the Session ID and automatically keep and track VIEWSTATE on the server for each user. Complex web applications with a lot of viewstate will render a little faster and run a little snappier. To implement, simply add a class with the code in Listing 1 to your web application (and you will need a .Browser file, covered in the next section.)

Listing 1: To use VIEWSTATE but leave it on the server, add a class file with the following code.

Listing 3 contains some simple sample code. Comment out the XML in bold for MyPageAdapter, run the code, and view source. You will see the fairly large VIEWSTATE. Uncomment the code—remove the <!-- --> comment characters—and run the code again. View the source. You will see that the VIEWSTATE is almost all gone. (See Listing 3 for some demo code.)

Listing 3: Some sample code you can use to test you PageAdapter.

Imports System.Collections.Generic
Partial Class _Default
Inherits System.Web.UI.Page
Protected Sub Page_Load(ByVal sender As Object, _
ByVal e As System.EventArgs) Handles Me.Load
If (Not IsPostBack) Then Return
Dim customers As List(Of Customer) = New List(Of Customer)
Dim I As Integer
For I = 1 To 100
customers.Add(New Customer(I, "Customer" + I.ToString()))
Next
GridView1.DataSource = customers
GridView1.DataBind()
End Sub
End Class
Public Class Customer
Private _iD As Integer
Public Property ID() As Integer
Get
Return _iD
End Get
Set(ByVal Value As Integer)
_iD = Value
End Set
End Property
Private _name As String
Public Property Name() As String
Get
Return _name
End Get
Set(ByVal Value As String)
_name = Value
End Set
End Property
''' <summary>
''' Initializes a new instance of the Customer class.
''' </summary>
''' <param name="iD"></param>
''' <param name="name"></param>
Public Sub New(ByVal iD As Integer, ByVal name As String)
_iD = iD
_name = name
End Sub
End Class

Right-click on your browser and select View Source. Search for VIEWSTATE to see the radical change in the amount of VIEWSTATE information with and without the PageAdapter.

Summary

I am a firm believer in user groups, TechEd, reading, and other such activities. Because I write, it's a little harder for me to find new things for me, but I do find them. Jeff Prosise demonstrated an implementation a PageAdapter and .Browser for ASP.NET 2.0 at TechEd 2007 in Orlando. (Jeff is one smooth presenter; if you get a chance, see him.) I hope you got to go. If not, try to make it next year.

About the Author

Paul Kimmel is the VB Today columnist for www.codeguru.com and has written several books on object oriented programming and .NET. Check out his new book UML DeMystified from McGraw-Hill/Osborne. Paul is an architect for Tri-State Hospital Supply Corporation. You may contact him for technology questions at pkimmel@softconcepts.com.

If you are interested in joining or sponsoring a .NET Users Group, check out www.glugnet.org.